Regional Anaesthesia

• Field Block- blocks the entire surgical field by infiltrating the nerve(s) supplying that region
  • Ring Block- a subtype of field block, usually applied to a digit or the penis, whereby everything distal to the block is anaesthetised.  (Note that adrenaline should NOT be used for ring block as it risks causing critical ischaemia to the affected area).

There are several regions which can be anaesthetised in this way.  For a more comprehensive list with where to inject, see the FRCA website here

• Brachial Plexus (upper limb/shoulder)
  • Interscalene block
    • Targets the trunks of the brachial plexus, achieving anaesthesia best in C4-7
    • Useful for shoulder surgery/relocation
  • Supraclavicular block
    • Targets the divisions of the brachial plexus, achieving anaesthesia best in C5-T1
    • Useful in arm surgery
  • Axillary block
    • Targets the cords of the brachial plexus, achieving anaesthetic best in C7-T1 (musculocutaneous nerve)
    • Useful in distal arm/hand surgery
• Femoral Nerve block
  • Anatomy
    • Arises from L2-4; runs deep to psoas in the groove between it and the iliacus muscle.  Lies on the iliopsoas as it passes under the inguinal ligament, lateral to the femoral artery (1cm at this point; 2cm at 1-2cm below the inguinal ligament).
  • Effect
    • Femoral nerve only (anterior thigh, knee and femur) OR ‘3 in 1’ block if using more anaesthetic and apply pressure distal to injection site (effects obturator and lateral cutaneous nerves too- i.e. most of the thigh)
• Sciatic Block
  • Arises from L4-S3 and exits under the biceps femoris muscle.  It then splits into the common peroneal and tibial nerves which run down the centre of the thigh.
  • There are several approaches to infiltrating the sciatic nerve (see FRCA)- although it can be found 2cm lateral to the ischial tuberosity at the level of the greater trochanter.
  • Useful for lower limb (ankle/foot) surgery; may be combined with femoral block for whole leg surgery
• Bier’s Block
  • This is IV regional anaesthesia, commonly used in the upper limb for distal fracture relocations/surgery
  • Method
    • Elevate the arm and then inflate a double cuff tourniquet over the upper arm to 300mmHg or 100mmHg above SBP (whichever is greater), effectively exsanguinating the arm.
      • There should be no radial pulse
    • Inject the anaesthetic (usually prilocaine) IV
    • To prevent pain, it may be suitable to inflate the lower cuff over the affected area after anaesthetisation, then release the upper cuff.
  • This requires close monitoring (of the cuff, the limb, and the patient) and the procedure should not last more than 45 minutes to prevent critical ischaemia
  • It is most commonly used for the relocation of Colles’ fractures.
• Intercostal nerve blocks
  • Can effectively choose any intercostal nerve.  Useful for anaesthetising one area for procedures e.g. chest drain insertion; or for pain relief e.g. flail chest/rib fracture.
  • IC nerves lie deep to internal and external intercostal muscles, and superficial to intercostalis intimis and the pleura.  The neurovascular bundle lies immediately inferior to the rib and consists of vein, artery and nerve (superior to inferior)
  • Method
    • Feel for the posterior angle of the rib at around the posterior axillary line and insert the needle at or just under the rib, ‘walking’ down the rib if necessary.  Once there, only advance 2-5mm more before infiltrating (aspirate beforehand to ensure not in IC vein/artery)

See also spinal and epidural

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